1. Field of the Invention
The present invention relates generally to the elimination of static electric charges on paper stock used within paper printing press machines, paper folding machines, paper collators, and other types of paper handling machines. More particularly, the invention relates to an apparatus and method which includes an air charge enhancement device to electrically charge air flowing in an air stream directed at statically charged paper stock used within these machines to discharge the paper stock.
2. Description of the Prior Art
In order to run a successful printing business and be competitive, it is essential to operate high capacity and high speed printing presses, collators and folders. The rate or speed of printing a high quality product can be significantly reduced by paper jams occurring within these machines. This type of problem most often presents itself when paper is fed into the machine and each sheet sticks together due to static electric charges building up due to friction between the sheet surfaces. Two sheets often stick together with two or more sheets then being fed into the printing press, resulting in a paper jam. This results in unwanted down time when the press is not operational. Since equipment can only run as fast as the paper will feed, it is necessary to eliminate as much static as possible between sheets of paper in the stack as they are fed into the machine. This elimination process tends to prevent these burdensome paper jams and misfeeds and the associated press "downtime."
All paper develops some electrical attraction between sheets to a varying degree. In particular, glossy heavyweight paper, used most often for magazines and brochures, is particularly troublesome. Since paper is an insulator and poor conductive material, any static charge which builds up between paper sheets tends to remain fixed on each sheet because it is not conducted away. The paper then exhibits characteristics similar to oppositely polarized magnets in which each sheet of a different polarity sticks or is attached together. A stream of air, in conjunction with a suction device, has most often been used to mechanically separate stock sheets for feeding within these machines. The top sheet is separated from the remaining paper stock, and is fed into the machine. The top sheet is separated by directing a stream of air from an air source to the side or front of the top sheet of paper stock. The airstream is of such a velocity that the air is directed between the top sheet and the remaining stock below. Each sheet often resists being separated because of the electrical attraction to the oppositely charged sheet below it. When a suction device attached to the machine attempts to lift and mechanically separate the top sheet for insertion into the machine, the attractive electrical force results in two or more sheets actually being inserted. This misfeed results in a jam because the machine detects the presence of more than one sheet and automatically shuts down.
As the paper begins to adhere or stick together, the machine must be slowed down. The stock must be continuously jogged and re-jogged or a compressor must be continuously used to blow the sheets apart from their side or back. In printing presses, typically, 81/2.times.11 carbonless sheets must be run one up on the A. B. Dick 360 instead of two up 11.times.17. Also, if using coated stock, smaller loads must be used in order to prevent sheet compression. Heavyweight carbonless stock must be used instead of the lightweight paper in order to prevent each sheet sticking due to the static electricity buildup. Overall, this means wasted time, slower press speeds, varying quality due to starts and stops, and small jobs taking much longer than necessary.
Many different techniques have been used to eliminate this type of static buildup in paper. These include the use of liquid sprays, tinsels, electric ionizers, nuclear ion cartridges, as well as re-trimming of the paper. None of these prior techniques have efficiently or consistently eliminated the static buildup problem.